Refrigeration evaporator coil with electric heating means



March 17, 1959 v. A. SCHULTZ 2,877,630

REFRIGERATION EVAPORATOR COIL. WITH ELECTRIC HEATING MEANS Filed May 20, 1952 2 j k k INVENTOR. Verna/1 4.56/711/72 ATTORNE Y United States Patent REFRIGERATION EVAPORATOR COIL WITH ELECTRIC HEATING MEANS Vernon A. Schultz, San Lorenzo, Calif. Application May 20, 1952, Serial No. 288,792

4 Claims. (Cl. 62-276) The present invention relates to improvements in an evaporator coil for a refrigerator, and its principal object is to provide means integrated into the coil for defrosting the latter.

More particularly, it is proposed to provide heating means inside of the coil in direct heat exchange with the refrigerant passing therethrough, so that the defrosting takes place from the insideout, attacking the frost first immediately adjacent the coil tube, where it is most difficult to remove, particularly in finned coils, and spreading to the outside, where the frost is comparatively easy to remove.

In the present invention, it is proposed to provide electrical heating means for the inside of the coil, and a number of problems have to be overcome in order to make electrical heating means suitable for the purpose.

In the first place, it is necessary to insulate the heating element with respect to the coil in such a manner that there will be no electrical contact between the heating means and any part of the coil, while, on the other hand, heat is freely transmitted to the refrigerant in the coil.

In the second place, the heating means will naturally have to be connected to a suitable outside source of power, and here again, the problem arises of providing suitable connections between the heater and the source of power, without allowing of leakage of the refrigerant from the coil.

In the present invention, it is proposed to arrange the heater in the coil in such a manner that the problems are solved, and that all changes of causing shorts in the electrical system or leakage in the refrigeration system are eliminated.

Further objects and advantages of my invention will appear as the specification proceeds, and the new and novel features of the same will be fully defined in the claims attached hereto.

The preferred form of my invention is illustrated in the accompanying drawing, forming part of this application, in which:

Figure 1 shows a fragmentary side view of an evaporator coil suitable for a refrigeration system, portions being shown in section to disclose interior construction; and

Figure 2, an enlarged section taken along line 2-2 of Figure 1.

While I have shown only the preferred form of my invention, it should be understood that various changes or modifications may be made within the scope of the claims hereto attached, without departing from the spirit of my invention.

Referring to the drawing in detail, the evaporator coil 1 may be of any suitable construction, and is here shown as comprising a number of lengths of tubing 2 arranged in parallel relation and formed with fins 3 in a conventional manner, the tubes being interconnected in a conventional manner, by means of U-shaped end members 4 arranged in a conventional manner to provide a conr. CC

tinuous coil through which a refrigerant may be passed from any suitable refrigeration system.

The novelty of the present invention consists in the introduction of electrical heating means 5 into the inside of the coil, the heating means preferably extending through the entire length of the coil.

In its preferred form, my heating means comprises a resistance wire 6, which may be made of a nickel chrome alloy, well-known in the art, and insulation 7 surrounding the wire, and a copper tube 8 surrounding the insulation.

The insulation is preferably made of material which is a good electric insulator, and at the same time, a good heat conductor. There are many materials available on the market for this purpose, such as magnesium oxide, an insulaticn known as neoprene, fiber glass or poly-vinyl plastic, and no invention is claimed for the particular material employed.

The tube 8 is preferably made of copper, but any other suitable metal will be satisfactory, as long as it can be fused, by welding, brazing, or soldering to the coil, at the points of entry and exit.

The total diameter of the tube containing the heating element should be considerably less than that of the coil tube, so as to offer little interference with the passing of the refrigerant through the latter.

The heating means may be introduced into the coil in any suitable manner, which will be readily understood by persons versed in the art, and the principal point of interest in the present invention is the manner in which the tube 8 is passed through the wall of the coil tubing, as at 9, at the point of entry and exit, and secured by welding, brazing, or soldering, or any process fusing the metals into an absolutely leak-proof joint.

It will be understood that the resistance wire, the insulation and the copper tubing 8 may be manufactured to form a unit for suitable assembly into the coil, as shown, or that, in other cases, the copper tubing 8 may be made an integral part of the coil, with the heating wire and insulation forming an independent unit adapted for sliding into the copper tubing 8.

It will also be understood that the ends of the wire 6 will be suitably connected to a source of power, and that the latter will be suitably controlled to effect the defrosting, either at manual operation, or automatically at periodic intervals, or in response to changes in pressure or temperature.

It will be noted that when the heating means is rendered active, it will heat the refrigerant directly, and the latter will transmit the heat to the coil and to the fins with a great deal of efficiency, since it immediately attacks the frost formed on the coil tube between the fins at the point where it is most difiicult to remove.

Frost about the outer portion of the fins usually drops off very easily in response to the diminished heating effect of the heating means reaching the outer portion of the fins.

I claim:

1. In an evaporator coil for a refrigerating system, a sinuous coil adapted to have a refrigerant pass therethrough, an interiorly unobstructed copper tube mounted inside the coil and following the curvature thereof and having ends projecting through the wall of the coil and forming leak-proof joints therewith, the tube having an outer diameter only a minor fraction of the inner diameter of the coil so as to make its resistance to the flow of the refrigerant substantially negligible, and the tube being open at both ends to allow a heating element to be passed therethrough for defrosting purposes.

2. In an evaporator for a refrigerating system, a sinuous coil adapted to have a refrigerant pass therethrough, an interiorly unobstructed copper tube mounted inside the coil and following the curvature thereof and having ends projecting through the wall of the coil and forming leak-proof joints therewith, the tube having an outer diameter only a minor fraction of the inner diameter of the coil so as to make its resistance to the flow of the refrigerant substantially negligible, and means for passing a heating medium through the tube for defrosting purposes.

3. In an evaporator for a refrigerating system, a sinnous coil adapted to have a refrigerant pass therethrough, an interiorly unobstructed copper tube mounted inside the coil and following the curvature thereof and having ends projecting through the wall of the coil and forming leak-proof joints therewith, the tube having an outer diameter only a minor fraction of the inner diameter of the coil so as to make its resistance to the flow of the refrigerant substantially negligible, and means for heating the tube from the inside thereof for defrosting purposes, the said heating means comprising a core of resistance wire and a cover for the core made'of material having electricity-insulating and heat conducting properties.

4. In an evaporator for a refrigerating system, a coil adapted to have a refrigerant pass therethrough, a copper tube mounted inside the coil and having ends projecting through the wall of the coil and forming leak-proof joints therewith, the tube having an outer diameter only a minor fraction of the inner diameter of the coil so as to make its resistance to the flow of the refrigerant substantially negligible, and means for heating the tube from he inside thereof for defrosting purposes, the said heating means comprising a core of resistance wire and a cover for the core made of material having electricityinsulating and heat conducting properties, and the cover for the core having an outer diameter considerably less than the inner diameter of the tube to provide clearance allowing of easy insertion and removal of the covered core into and out of the tube.

References Cited in the file of patent UNITED STATES PATENTS 

